Microwave sintering of AlN powder synthesized by a SHS method

Sintering of the AlN powder synthesized by a combustion synthesis method, which was developed recently by the present authors, was studied by using a microwave sintering technique. A single mode microwave cavity was used and an insulation package with a simple configuration was developed. A high sintering temperature (1900 °C or higher) and a stable and uniform heating were readily achieved. A temperature measurement technique using a thermocouple with extrapolation was established to obtain the sintering temperature. A percent theoretical density of 99.5% and a thermal conductivity of 186 W/m K were obtained for a specimen which was sintered at 1900 °C with a soaking time of 30 min and 3 wt.% of Y₂O₃ added. The effects of sintering aid (i.e., Y₂O₃) and sintering temperature on densification, microstructure and thermal conductivity of the sintered specimens were investigated.